title: PKCα and PKCδ regulate ADAM17-mediated ectodomain shedding of heparin binding-EGF through separate pathways.
abstract: Epidermal growth factor receptor (EGFR) signalling is initiated by the release of EGFR-ligands from membrane-anchored precursors, a process termed ectodomain shedding. This proteolytic event, mainly executed by A Disintegrin And Metalloproteases (ADAMs), is regulated by a number of signal transduction pathways, most notably those involving protein kinase C (PKC). However, the molecular mechanisms of PKC-dependent ectodomain shedding of EGFR-ligands, including the involvement of specific PKC isoforms and possible functional redundancy, are poorly understood. To address this issue, we employed a cell-based system of PMA-induced PKC activation coupled with shedding of heparin binding (HB)-EGF. In agreement with previous studies, we demonstrated that PMA triggers a rapid ADAM17-mediated release of HB-EGF. However, PMA-treatment also results in a protease-independent loss of cell surface HB-EGF. We identified PKCα as the key participant in the activation of ADAM17 and suggest that it acts in parallel with a pathway linking PKCδ and ERK activity. While PKCα specifically regulated PMA-induced shedding, PKCδ and ERK influenced both constitutive and inducible shedding by apparently affecting the level of HB-EGF on the cell surface. Together, these findings indicate the existence of multiple modes of regulation controlling EGFR-ligand availability and subsequent EGFR signal transduction.
authors.affiliation: Protein Phosphorylation Laboratory, Cancer Research UK, London Research Institute, London, United Kingdom. marie.kveiborg@bric.ku.dk
authors.forename: Marie
authors.initials: M
authors.lastname: Kveiborg
authors.forename: Rachael
authors.initials: R
authors.lastname: Instrell
authors.forename: Christina
authors.initials: C
authors.lastname: Rowlands
authors.forename: Michael
authors.initials: M
authors.lastname: Howell
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Parker
mesh_terms: D051722:ADAM Proteins / Q000378:metabolism* / Q000502:physiology; D000072198:ADAM17 Protein; D002478:Cells, Cultured; D016000:Cluster Analysis; D004357:Drug Synergism; D066246:ErbB Receptors / Q000819:agonists / Q000378:metabolism / Q000502:physiology; D066257:Heparin-binding EGF-like Growth Factor; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism*; D053858:Metabolic Networks and Pathways / Q000187:drug effects / Q000502:physiology; D010766:Phosphorylation / Q000187:drug effects; D051571:Protein Kinase C-alpha / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D051745:Protein Kinase C-delta / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D017434:Protein Structure, Tertiary / Q000187:drug effects / Q000502:physiology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: C587883:HBEGF protein, human; D066257:Heparin-binding EGF-like Growth Factor; D036341:Intercellular Signaling Peptides and Proteins; D047428:Protein Kinase Inhibitors; C512478:EGFR protein, human; D066246:ErbB Receptors; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D051722:ADAM Proteins; D000072198:ADAM17 Protein; C000606462:ADAM17 protein, human; D013755:Tetradecanoylphorbol Acetate